Hello. First time Land Rover owner. Bought an 03 Land Rover Discovery last night with 145k miles on it. I’m just learning about the rig so bear with me if I don’t have an answer to something.

So first, the engine has a slight ticking at idle. There are no signs of idling rough though. Once you start driving the tick goes away and it drives great.

Today I changed the oil and put full synthetic 10w30 in it. Then I bought and replaced the air filter and borrowed the OBD device from auto shop to check codes as the service engine soon light was on. Here are the codes it had in the bank;

- Oxygen sensor circuit bank 1 sensor 1
- P0171 Bank 1 system too lean
- P1171 no DTC definition found. See owners manual
- P1300 no DTC definition found. See owners manual
- P0301 Cylinder 1 misfire detected
- P0300 Random - multiple misfire detected
- P0308 Cylinder 8 misfire detected
- P0139 Oxygen sensor circuit slow. Response bank 1 sensor 2
- P0455 Evaporative Emission system. Leak detected (gross leak/no flow)

So obviously quite a few concerns. I reset the codes as I am not sure how long the car has sat. After about 15 mins and 2nd restart of motor the SES light came back on. So tomorrow I’ll see which codes are back.

My question is where should I start. Rigs in great shape look wise and aside from the tick at idle it drives well. Should I start with all the spark plugs? 02 sensors? Something else?

Thanks!!

Thanks for the replies. I’ll start here. I’m assuming switching to different oils to see what works best is ok to do? I’ll run with this oil while I do these repairs and see where I stand then try another oil.

Oh, do you recommend buying parts on Rock Auto or is there a better place to order you’d recommend?

Ok great, I’ll go with those NGK plugs and STI wires. Brakes feel great now and rotors look good. I might look into a good new set of tires this fall before winter, but I was happy to see brakes and tires looking ok when I bought it.

Thanks so much!